Powder inhalators of this type are provided with a supply member for containing powdered pharmaceutical drug for a large number of doses, a drug carrier with a measuring recess having a volume equivalent to one dose and an operation member for operating the drug carrier.
To inhale a powdered drug, the drug is loaded into the measuring recess from the drug discharge aperture of the supply member, and the drug carrier is then slid away from the supply member to move the measuring recess in a straight line.
During this movement, the powdered drug loaded into the measuring recess is scraped by one edge of the drug discharge aperture by the sliding action of the drug carrier, and a predetermined quantity of the powdered drug is conveyed into the inhalation channel (Japanese Patent Publication No. 2000-501013).
Such a configuration results in the following two problems.
First, when the powdered drug is scraped, a measuring recess 100 moves in a straight line as shown by the arrow in FIG. 42. As a result, the powdered drug accumulates in the illustrated shaded-area near the edge of a drug discharge aperture 101. As a result, the powdered drug becomes clogged between the supply member of the powdered drug and the drug carrier, which reduces the ability to measure the powdered drug and lowers the operating performance of the drug carrier.
Secondly, static electricity is generated due to friction when the drug carrier slides, and thus the powdered drug adheres to the inside of the powder inhalator. Consequently, the quantitative accuracy and particle containing ratio of the powdered drug is lowered.
The second problem may be solved by shortening the stroke of the measuring recess to reduce the amount of static electricity. However, it is difficult to reduce the amount of static electricity in the above-described conventional powder inhalator due to its configuration, as described below. More specifically, the conventional powder inhalator is configured so that a protecting cap also serves as the operation member and that the measuring recess moves by a distance equivalent to the stroke of the protecting cap in order to expose the mouthpiece. Thus, the measuring recess needs to move the distance that is required to remove the protecting cap from the mouthpiece of the powder inhalator.
Moreover, the operation member is required to move by a certain distance so as to give the user an appropriate feeling of operating the operation member even when a separate operation member is provided for operating the drug carrier. More specifically, the powder inhalator should be configured so as to indicate to the user that the powder inhalator is ready for inhalation through a recognizable operation feeling from the operation member because he/she cannot visually confirm that the measuring recess has moved into an inhalation channel to prepare the powder inhalator for inhalation.
As described above, it is difficult to reduce the amount of friction in a conventional powder inhalator by moving the operation member only a short distance due to its configuration.
The conventional powder inhalator is configured so that the drug carrier is operated by the operation member to convey the powdered drug loaded into the measuring recess toward the mouthpiece (Japanese Published Application No. 5(1993)-237189).
The conventional powder inhalator contains the supply member, the drug carrier, and other members in a housing. The operation member protrudes from the aperture of the housing to the outside to allow the user to manually operate the operation member. Therefore, a gap is created between the operation member and the aperture, and thus, the pharmaceutical drug becomes moistened due to external air flowing from the created gap.
The pharmaceutical drug can be protected against humidity by carrying the powder inhalator in a moisture-proof case, but this creates a need for the user to remove the powder inhalator from the moisture-proof case for every use. Thus, a considerable amount of time is required for the user to inhale the powdered drug. Moreover, portability is lowered by containing the powder inhalator in a moisture-proof case that is necessarily larger than the powder inhalator.
The present invention has been achieved in view of the above-described problems, and provides a powder inhalator which can prevent the powdered drug from becoming clogged between the supply member and the drug carrier, and further can reduce the amount of electrostatic charge without shortening the stroke of the operation member.
In addition thereto, the present invention provides a powder inhalator that has a high moisture-proof effect without employing a separate moist-proof case.